The present invention relates to multichip light-emitting-diode (LED) package, and more particularly, to a multichip LED package having a support member mounting two or more LED chips, one or more feedback sensors for measuring the quantitative and spectral characteristics of the LEDsxe2x80x2 light output, and digital signal processing circuitry including an analog-to-digital converter logic circuit for providing a digital signal output from the sensor(s) to a controller external to the package that controls the lumen output and color components of the LEDs.
Multichip LED packages have been used in the prior art as white light illuminating devices. For example, U.S. Pat. No. 5,136,483 to Schoniger et al. describes a white light illuminating device such as a headlamp, that employs red, green and blue LED""S that are used simultaneously and whose colors are complementary to each other to produce white light.
Another white light illuminating device is described in U.S. Pat. No. 5,803,579 to Turnbull, et al. The illuminating device in this patent includes a plurality of LEDs on a support member. When all of the LEDs are energized, illumination exhibiting a first perceived hue, e.g., blue-green, is projected from at least one of the LEDs and overlaps and mixes with illumination exhibiting a second perceived hue, e.g., amber, projected from at least one of the remaining LEDs. The overlapped and mixed illumination forms a white color.
A controller is usually used with these devices for at least xe2x80x9cturning-onxe2x80x9d and xe2x80x9cturning-offxe2x80x9d the LEDs. The light output and color of LEDs may also be adjustably controlled by the controller. This requires the use of some type of external optical sensor for sensing the lumen output and color (wavelength) of the device and providing this information to the controller.
The use of an external optical sensor undesirably increases the size and cost of the device. Moreover, there is no method for measuring the operating temperature of the LEDs in these existing devices. The operating temperature of the LEDs is important because changes in their operating temperature can effect the quantitative and spectral output of the LED, and therefore the device.
Accordingly, a multichip LED package is needed which substantially overcomes the disadvantages of the prior art multichip LED packages described above and provides further improvements in terms of cost, space, and manufacturing convenience.
A multichip light-emitting-diode package comprising a support member, at least two light-emitting-diode chips disposed on the support member, and at least one sensor disposed on the support member for reporting quantitative and spectral information to a controller relating to the light output of the light-emitting-diodes.
One aspect of the invention includes a signal processing circuit disposed on the support member for preparing the analog signal output produced by the sensors for digital processing by the controller.
Another aspect of the invention includes an analog-to-digital converter logic circuit which is provided in the signal processing circuit mentioned above, for converting the analog signal output produced by the sensors to a digital signal output.